1. Field of the Invention
The present invention relates to a truck for railroad car, and particularly to a truck for railroad car including an end beam for supporting an instrument.
2. Description of the Related Art
As a truck for railroad car, there is known one having an H-shaped, when viewed in plan, truck frame in which a transom is connected to intermediate portions, in a longitudinal direction of a railroad car, of side frames extending substantially in parallel at both right and left sides of a truck (for example, see JP-A-11-29040). In such a truck, from the necessity of supporting an instrument such as an antenna device, there is a case where an end beam (a beam extending in a lateral direction of the truck) is attached so as to connect the rear end portions (or front end portions) of the side frames, and the instrument is supported at the end beam.
Both end portions of the end beam as stated above are attached to the end portions (the rear end portions or front end portions) of the side frames of the truck. This attachment is typically performed by welding, or by bolt coupling. That is, the attachment of the end beam to the side frames is generally rigid connection.
When the end beam is rigidly connected to the side frames of the truck as stated above, there are disadvantages as described below.
Although a railroad on which a railroad car (truck) travels is constituted by two right and left rails, they are not always provided horizontally and in parallel according to the state of the ground on which the rails are installed. When they are not horizontal or in parallel as stated above, the relative positions of the right and left side frames of the truck are shifted in the vertical direction, and the truck frame is deformed such that the truck frame is deformed under torsion relative to the transom. In this deformation, although the amount of deformation of the truck frame near the transom is small, the amount of deformation of the truck frame near the end beam distant from the transom becomes large. Thus, in view of the fact that the amount of deformation of the truck frame near the end beam distant from the transom becomes large, it is necessary to increase the rigidity so that the stress generated at the end beam does not become larger than required, which causes an increase in weight of the truck frame.